Menard Bachy has carried out over the last 15 years a large number of groundwater containment structures utilising a wide range of geotechnical techniques. One particular technique is the Soil Bentonite (SSB)) wall which is one of the most efficient, cost-effective and environmentally friendly solutions to implement in – situ cut off (low permeability)) walls. SB walls have been utilised historically for a wide range of applications including confinement of contaminated groundwater around landfills, toxic tailing ponds but also for the improvement of performance of dams and other types of water retention structures. In the delivery of complex projects, SB walls have also been utilised in combination with other mechanical and hydraulic structures such as PVC membranes, hydraulic gates, leachate collection trenches, and sumps but also sheet piles and other retention systems.
For the particular case of sites presenting environmental challenges, involving soil and groundwater pollution, a strategy requiring both removal and treatment of the source of the contamination as well as control of the contaminated groundwater plume acting as the pollution carrier is required. In the case of urban excavations where treatment is complicated by access and impact on a community, contamination confinement is often preferred. In any case, the adopted strategy needs to take into account the future use of the site, combined solutions involving both the reduction of the source of pollution and control of the pollution carrier generally offer the most sustainable outcome.
This paper present s a range of projects performed in Australia and overseas utilising different forms of SB walls. A particular focus is given on project methodology, site validation and trial testing but also production and quality control. The paper also provides a comparison of the environmental impact that different cut off wall techniques have and how they compare with SB type walls.